One approach to support the communication requirements of the future includes utilizing optical interconnects, i.e. links, as an alternative to electrical wire-based interconnections. Currently, manufacturers produce products such as modules for optical interconnects and so-called optical cables. An optical module may be a transmitter (i.e. comprising a light source for transmitting an optical data signal), a receiver (i.e. comprising a photo detector for receiving an optical data signal) or a transceiver which is a combined receiver and transmitter. Often modules come with a connector for connecting one or more optical fibers for transporting the optical data signal. In an optical cable the module and fiber is typically pre-connected. It is also possible to have the module or the components of the module mounted directly on a circuit board, such as a motherboard for a computer for example for interconnects in a supercomputer or as a connection to peripheral equipment such as in the “Light Peak” and “Thunderbolt” technologies developed by the Intel Corporation.
In the context of the present invention an optical module refers in general to the system comprising optoelectronic components for transmitting or receiving an optical signal connected to driver and/or receiver electronics. Optoelectronic components are in the present context devices arranged to convert electrical energy into optical energy or optical energy into electrical energy, i.e. light sources and photo detectors such as laser diodes (often VCSELs) and photodiodes. Typically a module will also comprise an interface allowing the module to be connected to one or more optical fibers as well as control electronics to adjust the operating parameters of optoelectronic components. For example, operation of a laser diode typically requires an adjustable bias current, modulation current and optionally preemphasis. Often the modules will support more than one channel such as 2, 4, 8, 12 and 16 channels but any number of channels is conceivable depending on the application. For such use the light sources and photo detector are often available in arrays, such as 1×N arrays or 2×N where is N is a positive integer. Strictly, a 2×N array is referred to as a matrix, but in order to simplify notation these terms are used interchangeably.
In order to convert the electric data signal into a signal suitable for driving a light source to emit an optical signal comprising this data signal a driver circuit is required. Similarly a receiver circuit is required to convert the received optical signal to an electrical signal suitable for further transmission in the system. Such driver and receiver circuits are well-known in the art and they are typically provided as integrated circuits either as driver chips (comprising driver circuit(s)), transmitter chips (comprising driver circuit(s)), or transceiver chips (comprising a driver and receiver circuit(s)). In the context of the present invention the terms driver chip and transmitter chip are used interchangeably. A receiver chip may also be referred to as a TIA chip, a TIA+LIA chip or a TIALA the latter types explicitly mentioning the limiting amplifier which often a part of a TIA chip. The chips comprise data pins/pads for receiving/transmitting the electrical data signal to/from the host system (i.e. data pads are pads for connecting to the system side) and connecting pads for connecting to the optical devices (i.e. connecting pins/pads are for connecting to the optical side of chip i.e. light sources or photo detectors). In the present context the terms “pin”, bump, and “pad” are used interchangeably and refers in general to a connection node for external connection to the circuit on the chip.
The transmitter or receiver circuit may be divided into                channel circuit(s), which convert between the electrical data signal and the signal to/from the optical device sometime also referred to as the high-speed path,        auxiliary circuitry often comprises monitoring and/or control functions suitable for adjustment/surveillance of the performance and/or logical state of the channel circuit. It may also comprise circuitry and components such as voltage references, current references and thermometer. Other functions of the auxiliary circuitry may include functions to ensure eye safety, detection of valid data in the channel circuit(s) and RSSI (received signal strength indication). Often, the control circuit is accessible via a digital interface. In chips with multiple channels, i.e. having multiple channel circuits and connectors suitable for connecting to multiple optical devices, often at least a portion of the auxiliary circuitry is shared between the channel circuits.        